The results from this overall study analysis showed significant clusters or hotspots of cholera in Budiriro for the period under study. A total of 600 cases of cholera reported during the 10th of September 2018 to 2nd of October 2018 were included in the analysis. These included children and adults who all were residences of Budiriro. These were taken from the line list, which was recorded by the Harare City Health Department. We performed the Sat Scan, which reported high spatial-temporary clusters. Four high clusters purely spatial-temporary were detected and these were statistically significant (p < 0.05) (Table 1).
Table 1
Clusters detected from 05 September – 30 October 2018
Cluster | Dimension | Type | Number of cases | Radius | Starting date | Ending date | P-Value |
1 | Space-time | High | 57 | 0.22 km | 29/09/18 | 02/10/18 | 0.001 |
2 | Space-time | High | 105 | 0.55 km | 10/09/18 | 13/09/18 | 0.001 |
3 | Space-time | High | 7 | 0.059 km | 21/09/18 | 23/09/18 | 0.043 |
4 | Space-time | High | 5 | 0.16 km | 24/09/18 | 24/09/18 | 0.048 |
Cluster 1 had a relative risk of 3.10 from the 57 observed cholera cases. This cluster was detected from the period between 29/09/2018 to 02/10/2018 on the point location of 17,895836 S and 30, 935754 E with a radius of 0,22 km. This cluster was highly statistically significant with p-value = 0,001 since Sat Scan requires that p-values should be < 0.05 for it to be recognised as significant.
Cluster 2 covered a radius of 0,55 km and was the biggest cluster of the four clusters. Cluster 2 recorded 105 cholera cases during the period 10/09/2018 to 13/09/2018. The relative risk was 1.78 from the observed cholera cases. The p-value was statistically significant per Sat Scan (p = 0.001). Cluster 2 was point located on 17,893279s and 30,946710 E.
Cluster 3 was detected from the period 21/09/2018 to 23/ 09/ 2018, and over a duration 3 days with 7 confirmed cases of cholera. This cluster had a relative risk of 8.04 with a p value = 0.043. The location point of the cluster was on 17,877472 S and 30,931704 E covering a radius of 0,059 km.
Cluster 4 was the least significant cluster with a p-value = 0.048 and a relative risk of 13.25. The cluster was detected over one day on 24 September 2018. The cluster was located on 17,877472 S and 30, 931704 E covering a radius of 0,16 km. The Sat Scan was computed which spatially distributed the clusters or hotspots for cholera outbreak in Budiriro suburb. (Fig. 1
Table 1: Clusters detected from 05 September – 30 October 2018
Figure 1: Sat Scan map for spatial distribution of Budiriro cholera cases in 2018
Cartesian Coordinates Map further helped to show the geo-coordinates for the four hotspots in Budiriro suburb (Fig. 2). The google Map showed that there were three decommissioned boreholes that acted as a source of contamination. These are shown on the google map as HA034, HA039 and HA075. HA039 was in Cluster 3, HA034 was in Cluster 1 whilst HA075 was not in any Cluster for cholera. However, this borehole (HA075) acted as a source of transmission for cholera for Cluster 2 as it acted as the main source of water supply for the residences in Cluster 2 (Fig. 3). The boreholes were situated (HA039) at latitude − 17.8901 and longitude 30.9115, HA034 situated at latitude − 17.8972 and longitude 30.9366 while HA075 was at latitude − 17.8924 and longitude 30.9352. All these boreholes (HA034, HA039 and HA075) were identified by the Sat Scan to be less than 50metres from the sewage carriage that was reported to have a low flow rate. Within the residence, there was erratic treated water supply from council water sources. The sewage also experience frequent water shortage and had low flow rate. Borehole (HA075) was situated at the shopping centre. The shopping centre was within the residence and there were several public toilets at the shoping centre and nearer the borehole (HA075). HA039 was very close to a house (¬10 m) and falling short of being further away from a source (sewage carriage) of contamination. HA034 was in the residential area and close to sewage carriage.
Figure 2: Cartesian Coordinates Map showing location of hotspots for Cholera in Budiriro.
Figure 3. Map of Budiriro hotspots for cholera showing decommissioned boreholes marked on the map as HA.
We computed a Sat Scan map for the cholera hotspots which showed that Clusters 1, 2 and 3 were statistically significant (p < 0.05) and that there was high transmission of cholera within these clusters. Cluster 4 was not statistically significant (p = 0.602) (Fig. 4).
Figure 4. Sat Scan map for variances within clusters of cholera cases in Budiriro suburb.